It seems the error is related to the PayPal Auto-Login feature that is used in conjunction with the Express Checkout. Please try to follow the steps given here: 1. Log into your PayPal account. 2. Click on the gear icon on top to take you to the settings page. 3. Click on the Security tab on top. 4. Click on the Auto-Login option. 5. You will have a list of servers or IP addresses that you have authorized auto-login. Click on the Turn Off option to remove it. 6. if you do not know the IP you can turn off all the IP after that, you need to log in manually to PayPal account.